It has become commercially prudent to perform well service operations, such as formation testing and evaluation, in very deep wells using pressure controlled valve devices such as those taught by Upchurch in U.S. Pat. No. 4,796,699, entitled “Well Tool Control System and Method,” assigned to the assignee of this invention, the disclosure of which is hereby incorporated by reference into the specification of this application.
In U.S. Pat. No. 4,796,699 (hereinafter referred to as “Upchurch”), a well testing tool is disclosed which is not totally mechanical in nature. The tool includes a microelectronics package and a set of solenoid valves responsive to the microelectronics package for opening or closing a valve disposed in the tool. However, the well testing tool of Upchurch is susceptible to damage in extreme, harsh conditions.
For instance, debris or wear over time may damage the ball seats in the solenoid valves, causing leakage. Leakage may result in failure of the well testing tool, resulting in expensive and time consuming repair of the solenoid valves. Current solenoid valves require disassembly of the entire apparatus to redress the ball seat and replace multiple seals. Additionally, current solenoid valve seals are typically located both externally to the solenoid valve and internally in the solenoid valve and are difficult to repair and/or replace. Further, the complexity of disassembly and reassembly of the current solenoid valves may lead to misassembly errors. Misassembly errors include not properly aligning the solenoid valve at reassembly, cut or damaged seals, introduction of debris, and other errors well known in the art. These errors can lead to binding, leaking, and failure of the solenoid valve.
It is therefore desirable to provide a well tool control system and method for performing well service operations capable of withstanding harsh conditions, such as debris, high pressure and high temperature, and with ease of re-assembly in the event of wear or failure.